The present invention relates to a polymeric or polymer-based substrate for a magnetic hard disk recording medium, a magnetic hard disk recording medium comprising the polymeric or polymer-based substrate, and a hard disk drive system including a magnetic hard disk recording medium comprising the polymeric or polymer-based substrate. The invention has particular utility in the manufacture of lower cost magnetic hard disk systems for use in computer applications.
Magnetic media are widely used in various applications, particularly in the computer industry. A conventional longitudinal recording disk medium 1 used in computer-related applications is schematically depicted in FIG. 1 and comprises a non-magnetic metal substrate 10, typically of an aluminum (Al) alloy, such as an aluminum-magnesium (Alxe2x80x94Mg) alloy, having sequentially deposited thereon a plating layer 11, such as of amorphous nickel-phosphorus (NiP), a polycrystalline underlayer 12, typically of chromium (Cr) or a Cr-based alloy, a magnetic layer 13, e.g., of a cobalt (Co)-based alloy, a protective overcoat layer 14, typically containing carbon, e.g., diamond-like carbon (DLC) formed, as is known, by sputtering of a carbon target in an appropriate atmosphere or by ion beam deposition (IBD) utilizing appropriate precursor gases, and a lubricant topcoat layer 15, typically of a perfluoropolyether compound applied, as is known, by dipping, etc. The Co-based alloy magnetic layer 13 deposited by conventional techniques, e.g., sputtering, comprises polycrystallites epitaxially grown on the polycrystalline Cr or Cr-based alloy underlayer 12.
In operation of medium 1, the magnetic layer 13 can be locally magnetized by a write transducer or write head, to record and store information. The write transducer creates a highly concentrated magnetic field which alternates direction based on the bits of information being stored. When the local magnetic field produced by the write transducer is greater than the coercivity of the recording medium layer 13, then the grains of the polycrystalline medium at that location are magnetized. The grains retain their magnetization after the magnetic field produced by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The magnetization of the recording medium can subsequently produce an electrical response in a read transducer, allowing the stored information to be read.
Thin film magnetic recording media are conventionally employed in disk form for use with disk drives for storing large amounts of data in magnetizable form. Typically, one or more disks are rotated on a central axis in combination with data transducer heads. In operation, a typical contact start/stop (CSS) method commences when the head begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by the air flow generated between the sliding surface of the head and the disk. During reading and recording operations, the transducer head is maintained at a controlled distance from the recording surface, supported on a bearing of air as the disk rotates, such that the head can be freely moved in both the circumferential and radial directions, allowing data to be recorded on and retrieved from the disk at a desired position. Upon terminating operation of the disk drive, the rotational speed of the disk decreases and the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the disk. Thus, the transducer head contacts the recording surface whenever the disk is stationary, accelerated from the static position, and during deceleration just prior to completely stopping. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic sequence consisting of stopping, sliding against the surface of the disk, floating in air, sliding against the surface of the disk, and stopping.
Referring now to FIG. 2, shown therein, in perspective view, is a conventionally configured magnetic recording disk 30 having a CSS (i.e., landing) zone 36 and a data (i.e., recording) zone 40. More specifically, FIG. 2 illustrates an annularly-shaped magnetic recording disk 30 including an inner diameter 32 and an outer diameter 34. Adjacent to the inner diameter is an annularly-shaped, inner diameter CSS zone 36. When the disk 30 is operated in conjunction with a magnetic transducer head (not shown), the CSS zone 36 is the region where the head makes contact with the disk during start-stop cycles or other intermittent occurrences. In FIG. 2, the edge of the CSS zone is indicated by line 38, which is the boundary between the head landing zone 36 and the data zone 40 where information in magnetic form is stored within the magnetic recording layer of the disk.
It is considered desirable during reading and recording operations to maintain each transducer head as close to its associated recording surface as possible, i.e., to minimize the xe2x80x9cflying heightxe2x80x9d of the head. Thus, a smooth recording surface is preferred, as well as a smooth opposing surface of the associated transducer head, thereby permitting the head and the disk to be positioned in close proximity, with an attendant increase in predictability and consistent behavior of the air bearing supporting the head during motion. However, if the head surface and the recording surface are too flat, the precision match of these surfaces gives rise to excessive stiction and friction during the start-up and stopping phases of the cyclic sequence, thereby causing wear to the head and recording surfaces, eventually leading to what is referred to as xe2x80x9chead crashxe2x80x9d. Thus, there are competing goals of reducing head/disk friction and minimizing transducer flying height.
Conventional practices for addressing these apparent competing objectives involve providing a magnetic disk recording medium with a toughened recording surface to reduce head/disk friction by techniques generally known as xe2x80x9ctexturingxe2x80x9d. Conventional texturing techniques involve circumferential polishing or localized laser heating to create a xe2x80x9cbumpxe2x80x9d pattern with precisely defined features on the surface of a disk substrate, e.g., of Alxe2x80x94Mg alloy, to provide a texture thereon prior to subsequent deposition thereon of layers, such as an underlayer, a magnetic layer, a protective overcoat, and a lubricant topcoat, wherein the textured surface of the underlying substrate is intended to be substantially replicated in the subsequently deposited layers.
The continuing trend toward the manufacture of very low cost (e.g.,  less than $500) personal computers (PCs) necessitates a reduction in the cost of hard disk drives utilized in such computers. Accordingly, the use of lower cost materials, e.g., polymers, glass, ceramics, and glass-ceramics as replacements for the conventional Al-alloy based substrates for magnetic disk media has been proposed. However, only glass and glass-ceramic composite materials have been successfully utilized for the manufacture of practical disk drives. The extreme difficulty associated with grinding and lapping of glass and glass-ceramic composite materials have limited their use to only higher cost applications such as mobile disk drives for xe2x80x9cnotebookxe2x80x9d-type computers. Poor mechanical and tribological performance, track mis-registration (TMR) and poor flyability have been particularly problematic in the case of polymer-based substrates fabricated as to essentially copy or mimic conventional hard disk design features and criteria.
Accordingly, there exists a need for improved polymeric or polymer-based substrates suitable for use in the manufacture of hard disk magnetic recording media. In addition, there exists a need for improved hard disk drive systems including polymer substrate-based magnetic recording media utilized in conjunction with improved flying heads for providing optimum tribological performance comparable to, and at significantly lower cost than conventional Al alloy substrate-based hard disk drive systems.
The present invention addresses and solves the problems attendant upon the design, manufacture, and use of high recording density, hard disk magnetic media and systems incorporating same, while maintaining full compatibility with all mechanical aspects of conventional drive technology. Moreover, the present invention enables the manufacture of such hard disk magnetic media and disk drive systems at significantly reduced cost vis-à-vis conventional and manufacturing processes, thereby contributing substantially toward achieving the aim of manufacturing very low cost computers.
An advantage of the present invention is an improved substrate for a magnetic hard disk data recording/retrieval medium.
Another advantage of the present invention is an improved polymeric or polymer-based substrate for a magnetic hard disk recording medium.
Yet another advantage of the present invention is an improved magnetic hard disk data recording/retrieval medium.
Still another advantage of the present invention is an improved polymeric or polymer substrate-based magnetic hard disk recording medium.
A further advantage of the present invention is an improved magnetic hard disk drive data recording/retrieval system.
A still further advantage of the present system is an improved polymeric or polymer substrate-based magnetic hard disk drive system.
Additional advantages and other features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to one aspect of the present invention, the foregoing and other advantages are obtained in part by a substrate for a magnetic hard disk data recording/retrieval medium, comprising:
an annularly-shaped disk comprised of a polymeric or polymer-based material having inner and outer diameters and a pair of opposed major surfaces; and
a first, annularly-shaped region adjacent the outer diameter of at least one of the pair of surfaces and comprising a plurality of spaced-apart projections integrally formed therewith and extending therefrom, the first region forming a CSS or landing zone adjacent the outer diameter.
According to embodiments of the present invention, the disk has an outer diameter of from about 1.0 to about 4.0 inches and a rigidity or stifffiess at least equal to that of an about 20 to about 50 mils. thick aluminum (Al)-based disk of same outer diameter.
According to further embodiments of the present invention, the disk has a thickness of from about 60 to about 180 mils. and comprises at least one polymer selected from the group consisting of: polycarbonates, polyacrylates, polyesters, epoxy resins, polysulfones, polyether sulfones, polyimides, polyetherimides, and polystyrenes; the first, annularly-shaped CSS region or landing zone adjacent the outer diameter of the disk has a width of from about 50 to 150 mils.; each of the plurality of projections is integrally formed with the at least one disk surface by molding and forms a column from about 3 to about 10 xcexcm wide with a rounded upper surface, and extends for from about 50 to about 150 xc3x85 above the disk surface, with spacings of from about 8 to about 30 xcexcm between adjacent projections.
According to still further embodiments of the present invention, the substrate further comprises; a second, annularly-shaped region adjacent the inner diameter of the disk and comprising a plurality of depressions formed within one of the pair of disk surfaces, for use in clamping of the disk at the inner diameter thereof; and a third, annularly-shaped region intermediate the first and second annularly-shaped regions for forming a data/recording zone, the surface of the third, annularly-shaped region being textured.
According to another aspect of the present invention, a magnetic hard disk medium comprises:
an annularly-shaped disk comprised of a polymeric or polymer-based material having inner and outer diameters and a pair of opposed major surfaces;
a first, annularly-shaped region adjacent the outer diameter of at least one of the pair of surfaces and comprising a plurality of spaced-apart projections integrally formed therewith and extending therefrom, the first region forming a CSS region or landing zone adjacent the outer diameter;
a second, annularly-shaped region inwardly adjacent to the first, annularly-shaped region and forming a data/recording zone;
a stack of layers formed over at least the surface of the second, annularlyshaped region and comprising, in sequence from the surface thereof:
an underlayer;
a magnetic film;
a protective overcoat; and
a lubricant topcoat.
According to embodiments of the present invention, the layer stack extends over the surface of the first, annularly-shaped region, each layer of the layer stack replicates the surface contour of each of the plurality of projections; the medium further comprises a third, annularly-shaped region adjacent the inner diameter of the disk and comprises a plurality of recesses formed within one of the disk surfaces, for use in clamping of the disk at its inner diameter; and the surface of the second, annularly-shaped region forming the data/recording zone is textured and each layer of the layer stack replicates the surface contour provided by the texture.
According to yet another aspect of the present invention, a magnetic hard disk drive system comprises:
an annularly-shaped disk comprised of a polymeric or polymer-based material having inner and outer diameters and a pair of opposed major surfaces;
a first, annularly-shaped region adjacent the outer diameter of at least one of the pair of surfaces and comprising a plurality of spaced-apart projections integrally formed therewith and extending therefrom, the first, annularly-shaped region forming a CSS or landing zone for a head slider adjacent the inner diameter;
a second, annularly-shaped region inwardly adjacent to the first, annularly-shaped region and forming a data/recording zone;
a stack of layers formed over at least the surface of the second, annularly-shaped region and comprising, in sequence from the surface thereof:
an underlayer;
a magnetic film;
a protective overcoat;
a lubricant topcoat; and
a head slider positioned in proximity to the surface of the lubricant topcoat and including at least one slider pad comprised of a diamond like carbon (DLC) material facing the surface of the lubricant topcoat.
According to still another aspect of the present invention, a magnetic hard disk system comprises:
a magnetic hard disk recording medium comprising a substantially rigid polymeric or polymer-based substrate; and
head slider means in proximity to a surface of said medium for effecting storing and reading/out data/information stored in the magnetic medium.
Additional advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated for practicing the present invention. As will be described, the present invention is capable of other and different embodiments, and its several details are susceptible of modification in various obvious respects, all without departing from the spirit of the present invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as limitative.